My invention pertains to a vital voltage regulator and phase shift circuit arrangement. More specifically, the invention provides voltage regulator and phase shift apparatus for use with solid-state devices serving as track relays for alternating current track circuits on electrified railroads.
In electrified railroading, signal systems based on 100 Hz alternating current (AC) track circuits incorporating centrifugal motor type relays as track relays have been commonly used. One input for each track relay is connected to the track rails of the corresponding section, to be supplied with energy through those rails from the common 100 Hz AC track circuit source connected at the other end of the section while the second input is locally connected to the same source of track circuit energy. Systems using such track relays provide immunity against operation by the noncommercial alternating current propulsion energy, e.g., 25 Hz in one large electrified installation. It is also characteristic of such centrifugal relays to require approximately 68.degree. phase difference between the two signal inputs for operation of the relay armature. Since long track circuits of the 100 Hz type normally have on the order of 60.degree. phase angle lag in the track voltage at the receiver or relay end of the section, the phase difference between the track and local inputs to the centrifugal relay is sufficient to operate the relay when both signals are received, that is, when the track circuit is unoccupied. However, with a proposed conversion to commercial AC propulsion power, i.e., 60 Hz, the present centrifugal relays will not provide track circuit immunity from the propulsion energy. To continue use of the 100 Hz track circuit, which is desirable economically, a change in the track relay arrangement is therefore necessary. One such conversion arrangement is disclosed in my copending application for U.S. Pat., Ser. No. 953,527, filed Oct. 23, 1978, for a Vital Power Varistor Circuit for Railroad Signaling Systems, now U.S. Pat. No. 4,188,002 issued Feb. 12, 1980. This varistor circuit arrangement, and other proposed synchronous detector arrangements which may alternately be substituted for the centrifugal relay in the track circuit, require that the dual inputs be in phase. Therefore, a phase shift circuit for one signal input to the solid-state relay arrangement, preferably the local input signal, is required. Additionally, the varistor arrangement is a product device which also requires a regulated voltage input. Thus a voltage regulator is also required for proper operation and may be combined with the phase shift arrangement to provide a local input signal for the solid-state relay circuit arrangement having a regulated voltage and proper phase angle.
Accordingly, an object of my invention is a vital voltage regulator and phase shift circuit arrangement.
Another object of the invention is a vital circuit arrangement for regulating the voltage and phase of one input signal to a solid-state AC track relay.
Also an object of my invention is a vital voltage regulator and phase shift circuit apparatus for AC railroad track circuits to shift the phase of the local voltage input to the track relay means by a predetermined angle to match the phase angle shift of the track rail circuit input to that relay, so that the inputs are substantially in phase.
A further object of the invention is a vital circuit arrangement for regulating, within predetermined limits, the voltage level of the signal applied to one input of a dual input, solid-state AC relay arrangement and for shifting the phase angle of that signal to match the phase angle shift of the signal applied to the other input of the relay.
Still another object of my invention is an input circuit network for one input of a dual input, solid-state AC relay, including an energy source of selected frequency connected by a series LC filter to the primary winding of a saturable transformer, and a second LC filter coupling the secondary winding of that transformer to the relay load, for regulating the voltage and shifting the phase angle of the input signal to substantially match that of the signal applied to the relay second input which is received from a common source over a transmission line having a predetermined phase shift characteristic.
A still further object of the invention is a vital voltage regulator and phase shift arrangement for connecting one input of a solid-state track relay means to a local energy source in order to shift that input signal into phase with the track circuit input signal connected to the second relay input and further to regulate the voltage of the local input signal between predetermined limits to assure proper operation of the track relay means.
Other objects, features, and advantages of my invention will become apparent from the following specification and appended claims when taken in connection with the accompanying drawings.